For developing a power grid at the subsea, a number of electronic modules or apparatuses may be provided. The subsea apparatus may include a container that is pressurized in order to withstand the high water pressure below the sea level, such as 2000 m to 4000 m below sea level. The container or enclosure may hold one or more electronic devices, in particular a variable speed drive.
A variable speed drive may be a converter for converting in particular an AC-input power stream to an AC-output power stream, wherein, in particular, the frequency of the AC-output power stream may be controllable by the variable speed drive. Thereby, a number of actuators, such as a pump, a compressor, or the like may be driven by the variable speed drive. The enclosure or container needs to protect the enclosed electronic components or hardware components against the environment, in particular, the salty sea water. Further, the hardware or the electronic devices enclosed in the container may provide cooling during operation. Due to changes in the ambient pressure, in particular, water pressure, and due to changes of the internal temperature, (e.g., during operation of the electronic device), the enclosure may be needed to be volume compensated. Thereby, a volume compensator may be an expandable part of the enclosure that allows the volume to increase/decrease as a function of pressure and/or temperature changes. A bellow structure has been used as a conventional (e.g., volume) compensator for this purpose.
However, it has been observed that the use of a conventional compensator may not in all circumstances allow operation of the subsea apparatus in a reliable manner and may not enable monitoring the correct or saving operation of the subsea apparatus.
There may be a need for an arrangement for providing a variable volume size, for a container including such an arrangement and for a subsea apparatus including such a container, wherein monitoring is improved, thereby allowing to operate the system in a save manner. Further, there may be a need for a subsea apparatus, wherein it is enabled to monitor or detect the correct operation of the subsea apparatus, in particular enabling to detect a failure.